Coupling mechanisms of S–Fe–P in surface sediments under the stresses of high salinity and heavy metals in coastal rivers

Journal of Soils and Sediments - The aim of the study was to (1) investigate the distributions of sulfur (S), iron (Fe), and phosphorus (P) in coastal surface sediments under the stresses of high...     

Individual and additive effects of Na+ and Cl− ions on rice under salinity stress

This study was attempted to assess the extent of toxicity contributed by Na⁺ and/or Cl^? ions individually, besides their possible additive effects under NaCl using physiological and biochemical parameters. Despite the fact that most annual plants accumulate both Na⁺ and Cl^? under saline conditions and each ion deserves equal considerations, most research has been focused on Na⁺ toxicity. Consequently, Cl^? toxicity mechanisms including its accumulation/exclusion in plants are poorly understood. To address these issues, effects of equimolar (100 mM) concentrations of Na⁺, Cl^? and NaCl (EC ≈ 10 dS m^?1) were studied on 15-day-old seedlings of two rice cultivars, Panvel-3 (tolerant) and Sahyadri-3 (sensitive), using in vitro cultures. All three treatments induced substantial reductions in germination rate and plant growth with greater impacts under NaCl than Na⁺ and Cl^? separately. Apparently, salt tolerance of Panvel-3 was due to its ability to exclude Na⁺ and Cl^? from its shoots and maintaining low (<1.0) Na⁺/K⁺ ratios. Panvel-3 exhibited better vigour and membrane stability indices coupled with lower reactive oxygen species and lipid peroxidation levels, besides stimulated synthesis of proline, glycine betaine and ascorbic acid. Overall, the magnitude of toxicity was observed in NaCl > Na⁺ > Cl^? manner. Though Cl^? was relatively less toxic than its countercation, its effect cannot be totally diminished.     

Spatial and Temporal Variance of Metal and Suspended Solids Relationships in Urban Stormwater—Implications for Monitoring

Relationships between total suspended solids (TSS) and metals (Cu, Pb and Zn) were tested and compared amongst base and high flows of three urbanised catchments in Sydney Estuary, Australia. Significant relationships between TSS and Cu, Pb and Zn were detected for high flows within each catchment; however, no significant relationship was detected for TSS/Zn and TSS/Cu in one of the creeks (Whites Creek) and for TSS/Zn in another (Hawthorne Canal) in 2010 during base flow. Relationships between metals and TSS also varied significantly in locations of intercept and slope between high and base flow and amongst catchments. Spatial variance in TSS/metal relationships were likely caused by specific anthropogenic activities because land uses, meteorology and geology within the study catchments were similar. Results suggest TSS may be used as a surrogate for estimating metal loading in real time for urban catchments, once relationships between metals and TSS were established for individual catchments and for base and high flow conditions. Moreover, no differences in TSS/metal relationships were detected between 2009 and 2010 in Hawthorne Canal during high flow conditions, suggesting that this method of real-time monitoring may be reliable for assessing Cu, Pb and Zn loads during high flows over inter-annual periods. However, long-term consistency of TSS/metal relationships for base flow may need testing since changes in TSS/Zn and TSS/Cu relationships were detected between 2009 and 2010 in Hawthorne Canal. Although irregular discharges to stormwater did not conform to TSS/metal relationships, irregular discharges may be detected in real time by increased flow during dry weather conditions, which may facilitate regulation of these conditions that currently result in potential environmental harm to aquatic biota in Sydney Estuary.     

Long-term effects of intensive rice–wheat and agroforestry based cropping systems on build-up of nutrients and budgets in alluvial soils of Punjab,India

ABSTRACT

A detailed study was conducted to investigate the long-term effects of rice–wheat and poplar-based agro-forestry systems existing on a large area for last 25 years on the distribution of macro as well as micronutrients in surface soils, as well as their profiles. To achieve these objectives, profile soil samples (0–150 cm) were collected from 10 randomly scattered locations each from rice–wheat and poplar-based agro-forestry systems and analyzed for various physico-chemical properties. The results of our investigation revealed that pH, EC, OC available N, P and K reported significantly higher levels in agro-forestry as compared to rice–wheat system. On the other hand, DTPA-extractable and total Zn, Cu, Fe and Mn were significantly higher in D1 (0–15 cm), D2 (15–30 cm) and D3 (30–45 cm) depths of rice–wheat system which may be attributed to the reduced conditions prevailing during rice crop. Nutrient budgeting also assessed the impact of crop removal and fertilizer inputs along with recycling of crop residue and leaf litter. Also, the build-up of available nutrient status in surface layer (0–15 cm) and soil profiles (0–150 cm) continuously under these two systems helped in maintaining agricultural sustainability and soil fertility over a long period of time.     

Spatial and Temporal Variability of Soil Organic Carbon in the Corn Belt of Northeastern China, 1980s–2005: A Case Study in Four Counties

Estimates of changes and possible causes of regional soil organic carbon (SOC) are critical for evaluation of potential responses of terrestrial biosphere to global changes. A total of 382 soil samples, collected in the 1980s from four counties in the Corn Belt of northeastern China, and of 1,514 samples collected in 2005 from the same area, were examined for SOC concentrations. Spatial and temporal SOC concentrations were evaluated after the 25-year interval using geostatistics and kriging interpolation method. Results indicated that the average topsoil SOC concentrations of the study area increased from 1.24% in the 1980s to 1.47% in 2005. Spatial distributions of SOC in the two separate evaluations showed greater SOC concentrations in the middle part of the study area and lower SOC concentrations in the remaining areas. From the 1980s to 2005, SOC concentrations in the central part increased, whereas those in the northeastern and southwestern parts decreased. The increasing trend of SOC concentrations might be attributed to the land-use and land cover changes, crop productivity increase, and agricultural management.     

Quantifying effects of primary parameters on adsorption–desorption of atrazine in soils

Purpose

Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of atrazine in soils. Equilibrium batch experiments were carried out to investigate the adsorption–desorption characteristics of atrazine. The objectives of this study were to (1) determine and quantify the main soil parameters governing atrazine adsorption and desorption phenomena; (2) find the correlativity between the identified soil parameters; and (3) investigate the universal desorption hysteresis traits.

Materials and methods

Fifteen soils with contrasting physico-chemical characteristics were collected from 11 provinces in eastern China. The equilibrium time was 24 h both for adsorption and desorption experiments. Atrazine was detected by Waters 2695/UV HPLC.

Results and discussion

Adsorption isotherms of atrazine could be well described by the Freundlich equation (r?≥?0.994, p?<?0.01). The total organic carbon (TOC) was the first independent variable that described 53.0 % of the total variability of K _f, followed by the pH (9.9 %), and the clay (4.0 %) and silt (1.2 %) contents, separately; while the primary soil properties that affect desorption parameters included the TOC, pH, free Fe₂O₃ (Fe_d) and the sand content, with the biggest contribution achieved by the TOC (ranged from 48.5–78.1 %). The results showed that when the content ratio of clay to TOC (RCO) was less than 40, the atrazine adsorption was largely influenced by the organic matrix, while when the RCO was greater than 40, they were vital affected by the clay content.

Conclusions

Adsorption–desorption isotherms of atrazine in soils were nonlinear. The content of TOC, clay, and iron oxides, as well as the pH value were the key soil parameters affecting the adsorption–desorption of atrazine in soil, among which the RCO especially exhibited relevance. Additionally, the desorption hysteresis existed for atrazine retention in all 15 tested soils, and the hysteretic effect enhanced with the increasing time for desorption. This would be ascribed to the heterogeneity physical–chemical properties of these soils.     

Interactional effects of β-glucan, starch, and protein in heated oat slurries on viscosity and in vitro bile acid binding

Three major oat components, β-glucan, starch, and protein, and their interactions were evaluated for the impact on viscosity of heated oat slurries and in vitro bile acid binding. Oat flour from the experimental oat line "N979" (7.45% β-glucan) was mixed with water and heated to make oat slurry. Heated oat slurries were treated with α-amylase, lichenase, and/or proteinase to remove starch, β-glucan, and/or protein. Oat slurries treated with lichenase or lichenase combined with α-amylase and/or proteinase reduced the molecular weight of β-glucan. Heat and enzymatic treatment of oat slurries reduced the peak and final viscosities compared with the control. The control bound the least amount of bile acids (p < 0.05); heating of oat flour improved the binding. Heated oat slurries treated with lichenase or lichenase combined with α-amylase and/or proteinase bound the least amount of bile acid, indicating the contribution of β-glucan to binding. Oat slurries treated with proteinase or proteinase and α-amylase together improved the bile acid binding, indicating the possible contribution of protein to binding. These results illustrate that β-glucan was the major contributor to viscosity and in vitro bile acid binding in heated oat slurries; however, interactions with other components, such as protein and starch, indicate the importance of evaluating oat components as whole system.     

Spatial variation of nitrate–N and related soil properties at the plot-scale

Neglecting the spatial variation in soil nutrient status may result in unused yield potential and in environmental damage. Site-specific management has been suggested to reduce inappropriate fertilization that can adversely affect soil, ground and surface water. Decision criteria for determining variable-rate nitrogen fertilization are, however, lacking. This paper analyses the spatial variation of nitrate nitrogen (NO₃–N) and soil properties related to the N cycle at the plot-scale. Three 50×50 m plots were sampled in nested sampling designs of varying complexities. Classical statistics revealed a characteristic ranking in the variability of soil properties. Geostatistical analysis of the NO₃–N data from two plots showed that the small-scale variation found in one small subgrid was not typical for the small-scale variation in the entire plot, indicating bias in the sampling design. A trend component was found in the NO₃–N data and, consequently, the minimal requirement for the regionalized variable theory was not fulfilled. Problems due to design were overcome with a more complex nested sampling at the third plot. However, the spherical model fitted to the NO₃–N data of the first year explained only 21% of the total variance, whereas a pure nugget effect was observed in the second year. The water content data also showed a low structural variance, which was different in the two years. In contrast, two thirds of the variance of total carbon (C_t) and total nitrogen (N_t) could be explained by the fitted models. Seasonal variations, such as varying duration of snow cover, and extrinsic management effects, such as growing of a cover crop, may have contributed to the observed differences in variability between the years. Due to the low proportion of structural variance and the observation that spatial distribution was not stable with time, geostatistical analysis of NO₃–N and water contents data added only little information to classical statistical analysis. However, geostatistical analysis of total C and N contents provided a useful means to calculate spatial distribution patterns of these properties.     

Spatial and Temporal Variability in Dissolved Inorganic Nitrogen Fluxes at the Sediment–Water Interface in Lake Illawarra, Australia

In this study, benthic flux measurements of inorganic nitrogen (i.e., $ {\text{NH}}^{ + }_{4} $ , $ {\text{NO}}^{ - }_{2} $ ?+? $ {\text{NO}}^{ - }_{3} $ ) were made using a batch incubation system at different stations (i.e., shallow sandy macrophyte and unvegetated beds, and deep central mud) over four seasons in Lake Illawarra, NSW, Australia, to study the influence of different primary producers (i.e., seagrasses, microphytobenthos (MPB) and macroalgae) and/or different sediment types (i.e., sand or mud) on the benthic fluxes. In general, nutrient fluxes displayed typical diel variations, with lower flux out of sediments (release) or enhanced uptake by the sediment in the light, due to the photosynthetic activities of the plant-MPB-sediment community in Lake Illawarra during photosynthetic periods. A distinct seasonal pattern of inorganic-N fluxes was also observed (e.g., the marked difference between summers 2002 and 2003). This may be explained by the seasonal variations in the biomass and activity (growing or decay phases) of MPB, seagrass and macroalgae, which may influence their nutrient assimilation and alter the chemical conditions of surface sediments that influence the benthic geochemical processes and thus benthic nutrient fluxes. On an annual basis, unvegetated sediments displayed net DIN effluxes, while seagrass beds showed a net DIN uptake, and the highest DIN uptakes coincided with the largest standing crop of seagrass and/or macroalgae and the highest levels of benthic community production. This may be due to the enhanced denitrification and/or assimilation activity by rooted plants and macroalgae, and the effect is most efficient during periods of net growth (e.g., in Spring 2002).     

Biodegradation of litter in Eucalyptus pauciflora communities—I: Techniques for comparing the effects of fungi and insects

Intact leaves of E. pauciflora were confined either in litter bags of three mesh sizes (5, 1 and 0.5 mm) or 5 mm mesh size bags after treatment with benomyl, zineb, DDT or dieldrin to assess the effects of insects and fungi on decomposition. In the untreated material, there was a loss in dry weight and total phosphorus of about 45 and 60% respectively and an initial gain in total nitrogen of up to 10% followed by a loss of between 70 and 86% of the original amount. There was no significant difference between the effects of the mesh sizes. A different pattern was observed for the insecticide and fungicide treated leaves which suggested that the fungi tended to mineralize phosphorus but immobilize nitrogen while the insects tended to mineralize or remove by migration both phosphorus and nitrogen.     

The use of comprehensive two-dimensional gas chromatography and structure–activity modeling for screening and preliminary risk assessment of organic contaminants in soil, sediment, and surface water

Purpose

This article aims to investigate the use and benefits of using comprehensive two-dimensional gas chromatography (GC?×?GC) and structure?Cactivity relationship modeling for screening and prioritization of organic contaminants in complex matrices. The benefit of applying comprehensive screening techniques to samples with high organic contaminant content is primarily that compounds with diverse physicochemical properties can be analyzed simultaneously. Here, a heavily contaminated industrial area was surveyed for organic pollutants by analyzing soil, sediment, and surface water samples. The hazard of the pollutants were ranked using SARs.

Material and methods

The water samples were liquid?Cliquid extracted using dichloromethane and directly analyzed by GC?× GC?Ctime-of-flight mass spectrometry (GC?×?GC?CTofMS). Soil and sediment samples were extracted with dichloromethane in an ultrasonic bath and subjected to gel permeation chromatography to eliminate lipids and humic matter. The low molecular weight fraction was then analyzed with GC?×?GC?CTofMS.

Results and discussion

More than 10,000 components were found in each sample, of which ca. 300 individual compounds were unambiguously identified using the National Institute of Standards and Technology mass spectra library and authentic reference standards. Alkanes, polycyclic aromatic hydrocarbons, and phthalates were generally the most abundant and were found in all matrices. In contrast, chlorinated compounds such as chlorophenols, biphenyls, and chlorinated pesticides were only detected in samples from a few hotspot regions. The toxicities of the most frequently detected compounds and of the compounds detected at the highest concentrations in samples from hotspot regions were estimated by ecological structure?Cactivity relationships. The ratio of the measured concentration to the predicted toxicity level was then calculated for each compound and used for an initial risk assessment in order to prioritize compounds for further transport and fate modeling, complementary measurements, and more advanced risk assessments.

Conclusions

The advantage of using of GC?×?GC?CTofMS for preliminary screenings of contaminated areas was evaluated at a polluted area in northern Sweden. The area was found to carry organic pollutants such as polyaromatic hydrocarbons, aliphatic hydrocarbons, polychlorinated biphenyls, phthalic compounds, and many chlorinated pesticides. Preliminary risk assessments indicate which compounds to use for subsequent remediation experiments based on their availability on the site or toxicity.     

Distribution of Chemical Forms for Co, Cr, Ni and V in Typical Soils of China

Co,Ni,Cr and V in 25 typical soils of China were fractionated into exchangeable,carbonate bound (calcareous soils),Mn oxide bound,organically bound,amorphous Fe oxide bound,crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure,so as to study the distribution of chemical forms of these metals as well as the effects of soil proiperties on the distribution.The results showed that most of soil Co,Ni,Cr and V were present in residual forms,and the distribution ratio averaged 48.2% for Co,53.0% for Ni,81.5% for Cr and 68.7% for V.The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements.The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory,with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co,12.8% for Ni,6.6% for Cr and 7.2% for V.     

Spatial variation of soil test phosphorus and potassium,oxalate‐extractable iron and aluminum,phosphorus‐retention index,and organic carbon content in soils of Western Australia

Abstract

Spatial variation of bicarbonate soil test phosphorus (P) and bicarbonate soil test potassium (K) was studied by measuring soil test values for 40 individual soil samples collected from random locations within eight uniform 100 m by 100 m field sites in south‐western Australia. In addition, for five of the sites, spatial variation of the three P sorption indices (ammonium oxalate extractable iron, ammonium oxalate extractable aluminum, and the P retention index) and of organic carbon (C) was measured for 20 individual soils samples. Spatial variation was found to be large, with coefficient of variation (CV) exceeding 20% in most cases, and 50% in some cases. It is therefore essential to collect an adequate number of soil samples from uniform areas in paddocks in order to provide a representative composite sample to measure the soil properties.     

Climate changes and trends in phenology of fruit trees and field crops in Germany, 1961–2000

Distinct changes in air temperature since the end of the 1980s have led to clear responses in plant phenology in many parts of the world. In Germany phenological phases of the natural vegetation as well as of fruit trees and field crops have advanced clearly in the last decade of the 20th century. The strongest shift in plant development occurred for the very early spring phases. The late spring phases and summer phases reacted also to the increased temperatures, but they usually show lower trends. Until now the changes in plant development are still moderate, so that no strong impacts on yield formation processes were observed. But further climate changes will probably increase the effect on plants, so that in the future stronger impacts on crop yields are likely.     

Spatial distribution of glomalin-related soil protein and its relationships with root mycorrhization,soil aggregates,carbohydrates, activity of protease and β-glucosidase in the rhizosphere of Citrus unshiu

Relationships between the spatial distributions of glomalin-related soil protein (GRSP) and soil aggregates, carbohydrates or relevant enzymes are poorly studied. We found that two categories of GRSP, the easily extractable Bradford-reactive soil protein (EE-BRSP) and total BRSP (T-BRSP), respectively ranged between 0.3–0.6 and 0.5–0.8 mg/g DW soil, and these two BRSPs decreased with the increase of soil depth (0–40 cm) in the rhizosphere of a 22-year-old Citrus unshiu orchard. Both EE-BRSP and T-BRSP were significantly positively correlated with mycorrhization, 0.25–0.50 mm soil water-stable aggregates, water-extractable or hydrolyzable carbohydrates, and β-glucosidase, but significantly negatively correlated with protease. Our results demonstrate that the spatial distribution of GRSP is significantly affected by mycorrhization, soil carbohydrate, β-glucosidase and protease.     

The effects of straw return on potassium fertilization rate and time in the rice–wheat rotation

In order to investigate the effects of straw return on potassium (K) fertilizer application rate and time in the rice–wheat rotation, field experiments were conducted at three sites. The results showed that when the K rate was decreased to 70% of the recommended K dosage, crop yields showed no significant decrease. With K fertilization only at rice phase, crop yields showed no marked difference compared with that provided K fertilizer both at wheat and rice seasons. Though the NH₄OAc-extracted K and HNO₃-extracted K differed slightly among the treatments, the soil apparent K balance was negative without K fertilization. With crop straw fully incorporated, the recommended K dosage could be at least reduced by 30% at the experimental sites and the K fertilizer could be applied only at rice phase. A further hypothesis can be made that the best K rate was the amount of K took away by crop grain. In the long run, straw return combined with K fertilization would be an effective method to maintain soil K fertility and productivity.     

Land use effects on microbial biomass C, β-glucosidase and β-glucosaminidase activities,and availability,storage, and age of organic C in soil

Microbial biomass, β-glucosidase and β-glucosaminidase activities, and availability, storage, and age of soil organic C were investigated after 26 years of conversion from sugarcane (Saccharum officinarum) to forest (Eucaliptus robusta or Leucaena leucocephala), pasture (mixture of tropical grasses), and to vegetable cropping (agriculture) in a vertisol in Puerto Rico. Soil organic C (SOC) at 0–100 cm was similar under Leucaena (22.8 kg C/m²), Eucalyptus (18.6 kg C/m²), and pasture (17.2 kg C/m²), which were higher than under agriculture (13.0 kg C/m²). Soil organic N (SON) at 0–100 cm was similar under the land uses evaluated which ranged from 1.70 (under agriculture) to 2.28 kg N/m² (under Leucaena forest). Microbial biomass C (MBC) and N (MBN) of the 0–15-cm soil layer could be ranked as: pasture > Leucaena = Eucalyptus > agriculture. The percentages of SOC and SON present as MBC and MBN, respectively, were nearly 1% in pasture and less than 0.50% in forest under Leucaena or Eucalyptus and agricultural soil. The activity of β-glucosidase of the 0–15-cm soil layer could be ranked as: Leucaena = Eucalyptus > pasture > agriculture; while β-glucosaminidase activity was ranked as: Eucalyptus > Leucaena = pasture > agriculture. The soil δ ¹³C changed from 1996 to 2006 in forest under Eucalyptus (18.7‰ to 21.2‰), but not under Leucaena (20.7‰ to 20.8‰). The soil under Leucaena preserved a greater proportion of old C compared to the forest under Eucalyptus; the former had an increased soil mineralizable C from the current vegetation inputs. The soil under agriculture had the lowest enzyme activities associated with C cycling, lowest percentage of SOC as MBC, highest percentage of SOC present as mineralizable C, and highest percentage of MBC present as mineralizable C compared to the other land uses.     

Does white wine qualify for French paradox? Comparison of the cardioprotective effects of red and white wines and their constituents: resveratrol, tyrosol, and hydroxytyrosol

It is generally believed that the French paradox is related to the consumption of red wine and not other varieties of wine, including white wine or champagne. Some recent studies have indicated that white wine could also be as cardioprotective as red wine. The present investigation compares the cardioprotective abilities of red wine, white wine, and their principal cardioprotective constituents. Different groups of rats were gavaged with red wine, white wine, resveratrol, tyrosol, and hydroxytyrosol. Red wine and its constituent resveratrol and white wine and its constituents tyrosol and hydroxytyrosol all showed different degrees of cardioprotection as evidenced by their abilities to improve postischemic ventricular performance, reduce myocardial infarct size and cardiomyocyte apoptosis, and reduce peroxide formation. It was discovered in this study that although each of the wines and their components increased the enzymatic activities of the mitochondrial complex (I-IV) and citrate synthase, which play very important roles in oxidative phosphorylation and ATP synthesis, some of the groups were more complex-specific in inducing the activity compared to the other groups. Cardioprotective ability was further confirmed by increased expression of phospho-Akt, Bcl-2, eNOS, iNOS, COX-1, COX-2, Trx-1, Trx-2, and HO-1. The results of this study suggest that white wine can provide cardioprotection similar to red wine if it is rich in tyrosol and hydroxytyrosol.